KR20100017713A - Method of monitoring and inhibiting scale deposition in pulp mill evaporators and concentrators - Google Patents

Abstract

A method of monitoring and inhibiting scale precipitation and deposition from spent liquor in pulp mill evaporators and concentrators is disclosed. The method includes connecting a black liquor deposition monitor to a pulp mill evaporator or concentrator and measuring the thermal conductivity on the outer surface of the monitor. A controller interprets the measured thermal conductivity and determines a level of scale deposition. If the level of scale deposition is above a predetermined level, the controller is operable to introduce a scale-inhibiting composition to the spent liquor. The scale-inhibiting composition may include organic polycarboxylic acids; organic fatty acids; low molecular weight and polymeric aromatic acids; organic acid esters, anhydrides, and amides; low molecular weight and polymeric aliphatic and aromatic sulfonic acids; and low molecular weight and polymeric amines; and any combinations.

Description

METHOD OF MONITORING AND INHIBITING SCALE DEPOSITION IN PULP MILL EVAPORATORS AND CONCENTRATORS}

The present invention generally relates to a method for monitoring and inhibiting precipitation of scale. More specifically, the present invention relates to a method for monitoring and inhibiting the precipitation of scale from a spent liquor in an evaporator and concentrator of a pulp mill. The present invention relates in particular to a method for monitoring and inhibiting precipitation of scale in evaporators and concentrators of pulp mills to improve process efficiency in pulping operations.

Kraft pulping processes are one of the major pulping processes in the pulp and paper industry. Waste liquor (black liquor or “BL”) from the craft pulping process contains inorganic salts as well as various organic materials that are precipitates that degrade the efficiency of chemical recovery cycles. Inorganic pulping chemicals and energy are recovered by burning the BL in a recovery boiler. For efficient combustion in recovery furnaces, BL from pulp digesters with relatively low concentrations of solids is generally evaporated in a multistage process (i.e. multi-effect evaporator) and at least 60 It should be concentrated to% solids.

The alkaline pulping process differs from the kraft process in that sodium sulfide is not used in the alkaline pulping process, which results in less sodium sulfate in the waste liquid. In contrast, large amounts of sodium, ammonium, magnesium or calcium bisulfite are used in the sulfite process and produce high sulfate concentrations in the waste liquor. The neutral sulfite semichemical ("NSSC") process combines sodium sulfite and sodium carbonate. Although the ratios between the inorganic and scale-forming components differ for this process, the components are essentially the same.

Inorganic salts that form scale in the waste liquor of evaporators and concentrators have been one of the most persistent problems present in the pulp and paper industry. The concentrated waste liquor contains calcium, sodium, carbonate and sulfate ions at a level high enough to form a scale that precipitates out of solution and precipitates on the heated surface. The most important types of scales in evaporators are the hard scale (e.g. calcium carbonate (CaCO ₃ )) and the soft scale (e.g. bakeite 2 (Na ₂ SO ₄ ): Na ₂ CO ₃ )). The solubility of the two types of scale decreases with increasing temperature, which causes the scale to adhere to the heat transfer surface, greatly reducing the overall efficiency of the evaporator (Smith, JB & Hsieh, JS, Preliminary investigation into factors affecting second critical solids black liquor scaling. TAPPI Pulping / Process , Prod. Qual. Conf., Pp. 1 to 9, 2000 and Smith, JB & Hsieh, JS, Evaluation of sodium salt scaling in a pilot falling film evaporator . TAPPI Pulping / Process , Prod. Qual. Conf., Pp. 1013 to 1022, 2001; And Smith, JB et al., Quantifying burkeite scaling in a pilot falling film evaporator , TAPPI Pulping Conf., pp. 898 to 916, 2001).

Solubility of calcium carbonate in water is very low, while burkeite can be dissolved. Calcium carbonate precipitates form extensively at many stages of the papermaking process. Inhibiting calcium carbonate is another developed area outside of evaporator applications. On the other hand, bakite precipitated when the concentration of total solids reaches about 50% represents a particular problem of evaporators and concentrators. While bakate has a significant impact on productivity, neither monitoring methods nor chemicals exist that effectively suppress bakate.

It is very difficult to affect precipitation from supersaturated solutions of inorganic salts that are as water soluble as bakeite (see US Pat. Nos. 5,716,496, 5,647,955, 6.090,240). Sodium polyacrylate is known to act as a crystal-growth modifier for bakate (see European Patent No. 0289312). In addition, polyacrylic acid and methyl vinyl ether / maleic anhydride copolymers can act as inhibitors to soft scales (e.g., bakeite) (US patents). 4,255,309 and 4,263,092). Anionic / cationic polymer mixtures have also been proposed as scale inhibitors for evaporators (see US Pat. Nos. 5,254,286 and 5,407,583).

In general, monitoring inorganic scales is most efficiently accomplished using techniques in the quartz crystal microbalance ("QCM") family. However, the applicability of QCM-based instruments is determined by the crystal stability of the sensor under process conditions. Such equipment cannot be used under high temperature and / or high alkaline conditions. This limitation prevents the technique from being useful in digesters and evaporators. In addition to simple gravimetric techniques and non-quantitative features using Lasentec-FBRM®, laboratory techniques based on the accumulation of sediment on the heated surface have been proposed for waste liquids with solid contents in excess of 55%. There is no proposed method for use in waste liquor evaporators or concentrators under normal operating conditions.

Thus, there is a need in the pulp and paper industry to develop more efficient methods and alternatives for monitoring and inhibiting bakelite and other scale precipitation. Such suppression is particularly important in evaporators and concentrators in pulp mills.

The present disclosure provides a method for inhibiting and / or monitoring the precipitation of scale from waste liquor in an evaporator or concentrator of a papermaking process of a pulp mill. Types of scales generally include bakeite (soft scale), sodium sulphate and sodium carbonate (both are generally soft scale components), and in some cases, entrapped organic materials. Include. In one embodiment, the scale also includes a hard scale (eg calcium carbonate). The disclosed method is equally applicable in evaporators or concentrators of any type of pulp mill (eg, kraft, alkaline (ie soda), sulfite and NSSC plant operations).

The method includes measuring a change in thermal conductivity on the surface of a temperature-controlled sensor or probe. The thermal conductivity is determined by the level at which scale precipitation forms on the probe. In one embodiment, the thermal conductivity is measured only on the outer surface of the probe. The temperature-solubility dependency characteristic in the opposite direction of scale precipitation enables the application of techniques for monitoring such precipitation. The thermal conductivity is inversely proportional to the mass of accumulated precipitate.

In one embodiment, the method includes inserting a probe having a temperature-controlled outer surface into an evaporator / concentrator line of a pulp mill. In one embodiment, the method also includes measuring the thermal conductivity of the temperature-controlled outer surface. The thermal conductivity is determined by the amount of scale deposited on the temperature-controlled outer surface. The level of scale precipitation in the system is determined based on the measured thermal conductivity. In one embodiment, the measured thermal conductivity is transferred to a controller. According to one embodiment, if the level of the measured scale precipitation exceeds a predetermined level, an effective amount of scale-inhibiting component is added to the waste liquor.

In another embodiment, the present invention includes adding one or more scale-inhibiting or precipitation-inhibiting chemicals to the waste liquor. Exemplary chemicals include vegetable fatty acids; Organic fatty acids; Aromatic acids (eg, low molecular weight and polymerized aromatic acids); Organic polycarboxylic acids; Organic acid esters, anhydrides and amides; Low molecular weight, polymerized aliphatic sulfonic acid and aromatic sulfonic acid); Low molecular weight ingo polymerized amines; Poly (acrylic / maleic) acid; And any combination thereof. Unexpected synergistic effects were observed when using a mixture of vegetable fatty acids and poly (acrylic acid / maleic acid). Other preferred chemicals include certain “green chemicals” (eg, liquid mixtures of solid fatty acids and their esters or individual fatty acids (generally derived from bioproducts that include by-products of biodiesel products)). .

In one aspect, the present invention includes using a waste liquid monitor device to monitor precipitation of the scale. The apparatus includes a probe having a temperature control mechanism or means and a mechanism or means for measuring thermal conductivity on an outer surface of the probe. The thermal conductivity measured on the outer surface is related to the formation of precipitates on the outer surface. In one embodiment, the probe can be operated to deliver the measured thermal conductivity to the controller. In one embodiment, the device is temperature sensitive and the thermal conductivity on the exterior surface of the device increases as the level of deposits formed increases. The device is also expected to be used in the laboratory to test the efficacy of the scale inhibitor.

The low solids content (eg less than 55%) in the diluted BL does not limit the use of the device described in the process of the invention. The scale problem arises in waste liquors having a solids content of less than 50%, and without such limitations, it is an important feature of the present invention to be effective for BLs having a wide range of solids content typically found in evaporators and concentrators in pulp mills.

It is an advantage of the present invention to provide a method for monitoring precipitation of various types of scale from waste liquor in evaporators and concentrators in pulp mills.

It is a further advantage of the present invention to provide a method for inhibiting soft scale precipitation from waste liquor in evaporators and concentrators in pulp mills.

Another advantage of the present invention is to provide a method for inhibiting precipitation of hard scale from waste liquor in evaporators and concentrators in pulp mills.

Another advantage of the present invention is to prevent the loss of productivity efficiency in the evaporator of the pulp mill associated with the boilout caused by scale deposition and settling.

Another advantage of the present invention is to provide a method for continuously monitoring the effect of process changes on scale precipitation from waste liquors in evaporators and concentrators in pulp mills.

Another advantage of the present invention is to provide a method for continuously monitoring scale suppression program performance in evaporators and concentrators in pulp mills.

Another advantage of the present invention is to provide a method of monitoring the concentration of scale-inhibiting composition in the waste liquid using an inert fluorescence tracer.

Additional features and advantages are described herein and will be apparent from the detailed description and examples that follow.

In one aspect, the method includes an apparatus for monitoring soft scale in an evaporator and concentrator of a pulp mill. Although any suitable device is contemplated, the preferred device is a waste fluid or BL sediment monitor ("BLDM"). The BLDM probe is a metal (eg, stainless steel, alloy or any other suitable material) mounted on a heater and a heating controller (eg, electrical, electronic, solid state or any other heater and / or heating controller). Or a sensor. The thermal conductivity on the outer surface of the device changes relatively with scale precipitation. The temperature of the actual metal surface can be monitored and controlled. In one embodiment, the BLDM includes an outer metal sheath and a skin thermocouple embedded under the outer metal sheath. In one embodiment, the temperature of the probe is controlled and adjusted using components in a control panel. In a preferred embodiment, the BLDM is part of or connected to the controller.

"Controller system", "controller" and similar terms refer to passive operators or components (e.g., processors, memory devices, cathode ray tubes, liquid crystal displays, plasma displays, touch screens or other monitors). Refers to an electronic device having, and / or other components. In certain instances, the controller may be operated by integrating one or more specific-purpose integrated circuits, programs or algorithms, one or more wired devices and / or one or more mechanical devices. Some or all controller systems function at a central location (eg, network server) for communication with local area networks, broadband area networks, wireless networks, Internet connections, microwave links, infrared links, and the like. can do. In addition, other components (eg, signal conditioners or system monitors) may be included to facilitate signal-processing algorithms. In one embodiment, the controller is integrated into a control panel for the papermaking process.

In one embodiment, the control scheme is automated. In another embodiment, the control scheme is manual or semi-manual, and the operator reads the measured thermal conductivity signal and any chemicals (eg, dosage of scale-inhibiting composition, etc.) to be supplied to the waste line. Determine. In one embodiment, the measured thermal conductivity signal is read by a controller system that regulates the amount of scale-suppressive composition inserted into the system to maintain the measured rate of thermal conductivity change within a predetermined range or below a predetermined value. do. In one embodiment, the controller reads the signal and adjusts the amount of scale-suppressive composition that is inserted into the waste line to maintain the rate of change of the measured thermal conductivity.

Precipitation on BLDM is generally caused by a temperature gradient between the waste solution and the heated probe. Skin temperature is controlled using a controller that adjusts the input wattage for the probe, which exhibits a constant skin temperature profile under fixed conditions in an environment where no scale is formed. The skin temperature increases because the formation of deposits on the heat transfer surface is monitored. The scale layer creates an insulating barrier between the metal surface and the bulk water to prevent sufficient cooling, thereby raising the metal surface temperature. The skin heat conduction band of the probe is usually connected to a temperature controller / monitor connected to a data history recorder. In one embodiment, the probe includes a core heat conduction band connected to a temperature controller / monitor.

In one embodiment, the thermal conductivity is measured intermittently and transferred to the controller. In one embodiment, the thermal conductivity is measured continuously and delivered to the controller. In another embodiment, thermal conductivity is measured and delivered according to a predetermined timescale. In another embodiment, thermal conductivity is measured at one time interval and delivered at another time interval. In other embodiments, the thermal conductivity can be measured and delivered in any suitable form.

In one embodiment, the present invention includes a method for inhibiting deposition and precipitation of scale from waste liquor in an evaporator or concentrator of a pulp mill. "Spent liquor" means black liquor (BL) from the operation of a kraft, alkaline, sulfite or neutral sulfite semi-chemical ("NSSC") plant. The scale may include bakate, sodium sulfate, sodium carbonate and entrapped organic material. Other scales may include calcium carbonate and / or organic material. It is anticipated that the method may be practiced to suppress any type of scale in various other systems.

Under circumstances where the amount of scale is measured to the extent that the scale-inhibiting composition is added, the method includes inserting an effective amount of the scale-inhibiting composition into the waste liquid. The composition may comprise one or more compounds (eg, organic mono- and polycarboxylic acids (eg, fatty acids, low molecular weight and high molecular weight aromatic acids); polymerized aromatic acids; organic acid esters, anhydrides and amides; low molecular weight And high molecular weight polymerized aliphatic sulfonic acids and aromatic sulfonic acids; low molecular weight and high molecular weight polymerized amines, and the like.

The acid can be used “as is” or in the form of precursors and forms acidic functions when exposed to the environment of the process. Exemplary precursors include esters, salts, anhydrides or amides. These compounds may be used in combination and in some mixing cases may have a synergistic effect. For example, examples of mixing may include maleic / acrylic acid copolymers mixed with fatty acids and / or fatty acid esters as illustrated in the examples below.

In one embodiment, the fatty acids and / or fatty acid esters are derived from a biodiesel manufacturing process. In some steps during the manufacture of biodiesel, including natural glycerin-treatment steps, inexpensive by-products can be produced. Such byproducts can also be produced in transesterification reactions involving triglycerides. Such by-products are generally mixtures of fatty acids and fatty acid esters. For example, the ratio of fatty acids to fatty acid esters may be 1: 1, with a viscosity suitable to be fed to the waste liquor using standard equipment. According to one embodiment, fatty acid by-products can be derived by adding an acid to the fatty acid salt solution in a natural fatty acid alkyl ester step during the process of making biodiesel. Alternatively, it can be derived by adding acid to the fatty acid salt solution in the natural glycerin stage. For example, the fatty acid by-product can be derived by adding acid to the bottom effluent of the esterification stage and / or adding acid to the wash water (eg, soapy water) of the ester product.

Fatty acid by-products may also be derived by adding acid to any biodiesel manufacturing process stream containing components of one or more fatty acid salts. For example, an acid is added to a fatty acid salt solution in a natural fatty acid alkyl ester step; Adding acid to the fatty acid salt solution in the natural glycerin stage; And acid addition to the stream of one or more biodiesel manufacturing processes containing components of one or more fatty acid salts.

In one embodiment, the fatty acid byproduct comprises about 1 to 50 weight percent of one or more methyl esters and about 50 to about 99 weight percent of one or more fatty acids. According to another embodiment, the fatty acid by-products include one or more methyl esters, organic salts, inorganic salts, methanol, glycerin and water. The remaining ingredients may include, for example, unsaponifiable matter.

It should be understood that the derived methods described above are exemplary and not intended to be limiting. For example, US patent application Ser. No. 11 / 355,468, entitled "Fatty Acid Byproducts and Methods of Using Same," is incorporated by-product of the biodiesel manufacturing process. It provides a more detailed description.

Exemplary free fatty acids derived from biodiesel by-products include palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid. , Linolenic acid, arachidic acid, eicosenoic acid, behenic acid, lignoceric acid, tetracocenic acid, tetracosenic acid and the like and combinations thereof It includes. The fatty acid by-products generally comprise one or more saturated and unsaturated fatty acids of C6 to C24, saturated fatty acid salts and unsaturated fatty acid salts of C6 to C24, methyl esters, ethyl esters and the like and combinations thereof. The fatty acid byproduct may further comprise one or more components (eg, C 1 to C 6 mono-, di- and tri-hydric alcohols and combinations thereof).

In another embodiment, suitable fatty acids and alkyl esters are derived from tall oil stock, a wood processing by-product. Typical tall oil fatty acid stocks include about 1% palmitic acid; About 2% stearic acid; About 48% oleic acid; About 35% linoleic acid; About 7% of conjugated linoleic acid (CH ₃ (CH ₂ ) _X CH = CHCH = CH (CH ₂ ) _Y COOH, wherein x is generally 4 or 5, y is generally 7 or 8, X + Y is 12); About 4% of other acids (e.g., 5,9,12-octadecatrienoic acid), linolenic acid, 5,11,14-aicosartranoic acid (5,11, 14-eicosatrenoic acid), cis, cis-5,9-octadecadenoic acid, eicosadienoic acid, elaidic acid, cis-11 octadecanoic acid, and C-20, C-22, C-24 saturated acid); And about 2% unchecked.

In one embodiment, the scale-inhibiting composition comprises an organic carboxylic acid (eg, a 1: 1 ratio of acrylic acid-maleic acid copolymer, having a molecular weight of about 1,000 to 50,000). In one embodiment, the composition comprises individual carboxylic acids or mixtures of fatty acids and / or fatty acid esters having a chain length of about 5 to about 50, and may be derived from biodiesel by-products as described above. In one embodiment, the composition comprises an ethylene-vinyl acetate-methacrylic acid copolymer having a molecular weight of about 1,000 to about 50,000. In another embodiment, the composition includes phthalic acid and other aromatic vic-dicarboxylic acids. In another embodiment, the composition comprises one or more linseed oil-derived polymers. Suitable flaxseed oil-derived polymers are prepared by optionally adding pentaerythritol-mediated crosslinked and thermally polymerizing flaxseed oil in the presence of maleic anhydride.

In one embodiment, the scale-inhibiting composition comprises an organic acid anhydride or amide. Exemplary anhydrides or amides are mono- or dicarboxylic acid anhydrides (eg, octadecenyl / hexadecenyl-succinic anhydride), octadecenyl / isooctadecenyl-succinic anhydride, fatty acids Anhydride mixtures, 1,8-naphthalenedicarboxylic acid amide, polyisobutenyl succinic anhydride and the like and combinations thereof. Suitable polyisobutenyl succinic anhydrides generally have a molecular weight ranging from about 400 Da to about 10 kDa.

In one embodiment, the scale-inhibiting composition comprises sulfonic acid (e.g., styrenesulfonic-maleic acid copolymer in a 1: 1 ratio, having a molecular weight of about 1,000 to about 50,000). do. In one embodiment, the sulfonic acid is a sulfonated naphthalene-formaldehyde condensate. In another embodiment, the sulfonic acid is alkyl-sulfonic acid or alkenyl-sulfonic acid having an alkyl chain of about C5 to about C24.

In another embodiment, the scale-inhibiting composition comprises an amine (eg, linear or cross-linked polyethyleneimine having a molecular weight of about 1,000 to about 100,000). In one embodiment, the amine is a carboxymethyl or dithiocarbamate derivative of linear or cross-linked polyethyleneimine having a molecular weight of about 1,000 to about 100,000. In one embodiment, the amine is an N-vinylpyrrolidone-diallyldimethylammonium copolymer. In another embodiment, the amine is 4-piperidinol (eg, 2,2,6,6-tetramethyl-4-piperidinol (2,2,6,6-tetramethyl) -4-piperidinol) or any other aliphatic amine or cyclic amine).

Without being bound by any particular theory, esters, anhydrides, and amides of certain organic acids have been theorized to account for activity due to the rapid hydrolysis and release of free acids. Furthermore, the activity of the sulfonic acids and amines described above was not expected. Their mechanism of action is different from that of carboxylic acids and can therefore be used as a component of the composition with a synergistic effect or as a composition of its own. For example, the combination of acrylic acid-maleic acid copolymer and fatty acid / ester is the same as due to polycarboxylates (blocked crystal growth) and other mechanisms of long-chain fatty acids / esters (increased aggregation in solution volume). Silver particles reduce the likelihood of precipitation on the surface). It should be understood that all possible combinations of chemicals of the abovementioned types can be used.

In other embodiments, the temperature range in the evaporator or concentrator of the pulp mill may be wide. For example, in certain applications the temperature of the waste liquid may be about 90 to about 120 ° C., and the temperature gradient between the waste liquid and the heated probe is about 70 to about 80 ° C. For the probe a temperature of about 170 to about 190 ° C. is preferred, with a temperature range of about 180 to about 185 ° C. more preferred. Typical flow rates for evaporators or concentrators in pulp mills are from about 0.5 to about 3 gallons per minute (gal / min). The concentration gradient is influenced by the flow rate and the temperature of the waste liquor and is generally adjusted for each application. The flow rate and composition of the waste liquid affects the transfer of material and heat to / from the heated surface of the probe. Thus, the settling time (i.e. accumulation of precipitate) and the set temperature gradient are appropriately adjusted. These parameters are specific to particular evaporator conditions and must be determined experimentally or theoretically for each application. A constant flow rate is generally maintained by an automatic flow regulator (eg, back pressure regulator).

The preferred range of scale-inhibiting compositions for treating waste liquor is from about 1 to about 2,000 parts per million (ppm) based on the waste liquor. More preferred dosage is about 20 to about 1,000 ppm. More preferably, the dosage ranges from 50 to about 500 ppm based on waste fluid.

In another embodiment, monitoring the dosage and concentration of the composition in the system includes using a molecule (ie, tracer) with a fluorescent moiety or an absorption moiety. Such tracers are generally inert and added to the system at known rates in the scale-inhibiting composition. As used herein, "inert" refers to any other chemical or other system parameter (eg, temperature, pressure, alkalinity, concentration of solids, and / Or other parameters) is not significantly or significantly affected. "Not significantly or significantly unaffected" means that the inert fluorescent compound has a change that does not exceed about 10% in the fluorescence signal under conditions normally present in the waste fluid.

Exemplary inert fluorescence tracers suitable for use in the methods of the invention include 1,3,6,8-pyrenetetrasulfonic acid, tetrasodium salt (CAS registration). No. 59552--10-0); Monosulfonated anthracene and salts thereof, including but not limited to 2-anthracenesulfonic acid sodium salt (CAS Registry No. 16106-40-4) dmf; Disulfonated anthracenes and salts thereof (US Patent Application 2005/0025659 A1 and US Patent 6,966,213 B2, each of which is incorporated herein by reference in its entirety); Other suitable fluorescent compounds; And combinations thereof. Such inert fluorescence tracers are the trade name TRASAR® commercially available from Nalco Company, Naperville, Ill., Or can be synthesized using techniques known to those with average knowledge in the art of organic chemistry.

Monitoring the concentration of the tracer using absorbance or fluorescence allows for precise control of the dosage of the scale-inhibiting composition. For example, fluorescence signals of inert fluorescent chemicals can be used to measure the concentration of scale-inhibiting compositions or compounds in the system. The fluorescence signal of the inert fluorescent chemical is used to determine whether a desired amount of scale-inhibiting composition or product is present in the waste fluid, whereby the supply of the composition is controlled to ensure that the desired amount of scale-inhibitor is in the waste fluid. Can be. Monitoring the concentration of the fluorophore series ensures the nature of the comprehensive system.

Example

The foregoing may be better understood with reference to the following examples, which are for illustrative purposes and are not intended to limit the spirit of the invention.

Specified test protocol

Synthetic bakate saturated BL was prepared by dissolving anhydrous sodium carbonate / sodium sulfate of 1: 2.68 (weight ratio to weight ratio) premixed at about 40% BL for 3 hours (50% to reduce viscosity). Diluted with BL). 1.5 kg of anhydrous solid mixture was used for each 5-liter sample. After resaturation with a synthetic bakate of solid, the solution was reused. The BL of the bakate-saturated synthesis was preserved until all solids precipitated out of solution, after which the solution was decanted.

Testing the deposition and sedimentation of the bakate included placing 600 ml samples of the synthetic bakite-saturated BL in a stainless steel cylinder equipped with a heat conduction band and a heating element. The heating element was a rod heated to 100-watts of stainless steel. The rod was heated to full force for 20 minutes to allow the sample to reach a final temperature of about 95 ° C., removed from the cylinder, and then cooled in air. The bakite precipitate on the rod was mechanically removed from the surface of the rod, dried at 105 ° C. and weighed. % Inhibition (“% I”) was determined by weight and each sample was normalized by comparison with the control according to the following formula:% I = 100 × ([control]-[sample]) / ([control] ]).

Sediment Monitor ("BLDM") test protocol from BL

A BL circulation system (available from M / K Systems, Inc., Bethesda, Maryland) with a 6-liter digester was set up and connected to BLDM. The main component of the BLDM device is a heated mild steel 3/8 × 6 inch probe with a heat flux of up to 138 kBtu / hr-ft ² (watt density 254 W / in ² ). It was. The skin heat conduction band was embedded under the cover of the outer metal and adjusted according to the heat transfer length. The actual metal surface temperature was monitored and the power of the heated probe was controlled and controlled using the control panel of the machine.

Skin thermocouples were connected to a temperature controller submerged in a MadgeTech data collector (available from MadgeTech, Inc., Warner, New Hampshire). A core heat conduction band was connected to the temperature controller. The solution was pre-heated and the probe itself maintained at temperature. The two heat conduction zones should monitor the water at the inlet and outlet of the probe to ensure that the flow of water is fast enough to prevent the water from boiling.

Precipitation on the BLDM probe is caused by a temperature gradient between the solution and the probe, and the skin temperature is controlled using a Eurotherm 2200 Series controller that controls the amount of watts input to the probe. The skin temperature was kept constant under fixed conditions in an environment where no scale was formed. Under the conditions in which the precipitate is formed, the device indicated an increase in skin temperature because of thermal insulation due to the effect of the precipitate, which prevented heat exchange between the metal surface and the bulk solution.

The test solution was a synthetic bakate-saturated BL as mentioned above. The solution can be used again after being resaturated with 500 g of solid bakate. At the end of the saturation process each test solution was added with other inhibitors shown in the table below and mixed well. The flow was maintained at 0.75 to 1.0 gpm. The water was placed in an immersion heater fmf digester to boil the water so that the heating element was completely immersed and the wall was not touched. The solution was preheated at 43 ° C. to 45 ° C., with the heater removed and the lid closed. Power was applied at 17% and data collected at 1 minute intervals.

In the calcium carbonate test, the test solution was a pulp mill BL (about 25% solids). Another inhibitor was added to each test solution and mixed well and maintained at a flow of 0.5 gpm. The solution was preheated to 101 ° C. (lid closed). The power was applied and the skin temperature was initially at 170 ° C. Calcium chloride solution of 0.1% (based on Ca ^{2 +} ion) was administered to the first speed in ml / min for 90 minutes. Data was collected at 1 minute intervals.

BLDM was used to test selected chemicals under laboratory conditions. The results are generally consistent with the specified test protocol, but more realistically represent the scale process in the evaporator. Thus, both tests used the same active chemicals, while the BLDM test made a smaller difference. This test showed a synergistic effect between AM and fatty acids. Optimal results were achieved with compositions of AM / fatty acid of 1: 1. Without mixing this chemical, no single product was formulated. However, when fed separately, they were more readily dissolved (AM) or dispersed (fatty acid / fatty acid ester composition) in hot BL. In individual experiments, selected chemicals have been shown not only to inhibit bakate precipitation but also to inhibit individual components, sodium carbonate and sodium sulfate.

In field tests, BLDM was installed after the first effect pump (about 50% solids-samples of precipitate from the same site were identified as bakate earlier by analytical data). The instrument was connected to a system arranged sidestream using a 50-ft curved hose past the feed system providing sufficient mixing and residence time. BL returned to the second effect evaporator line. The two products for testing, FA / FAME and AM, were easily mixed in the BL but did not mix, thus installing two separate supply systems.

Bakeite precipitation occurred on the BLDM sensor from the effect evaporator BL and a reproducible baseline was recorded. Accumulation occurred slowly with significant induction period. It is not recommended to apply excessive power to promote fouling or sedimentation because the probe temperature increases exponentially after the induction period. In addition, pyrolysis of organic materials on heated surfaces should be avoided, and the best practice is to apply minimal heat. The optimum initial temperature for this test was found to be about 183 ° C. The rate and pattern of settling depend on the nature of the BL, which is initially slow, but gradually increases the temperature response of the probe.

 Because of the nature of the monitoring technique (temperature-induced precipitation), it should be emphasized that the "exponential" response of the instrument at the end of the experiment does not mean exponential growth of the sediment-that is, it indicates that it has crossed the fork. . The standard test lasts about 1 day. Mild conditions provide better differences but take longer. In subsequent tests, the precipitate was collected from the surface of the probe and analyzed. According to the analysis, the precipitate was 70% bakeite. Inhibition of the bakate scale was tested above by two compounds (FA / FAME and AM) and mixtures thereof were observed. Both compounds showed good performance and mixtures thereof were shown to have synergistic effects (Examples 8 and 9).

Examples 1-6 show the results of selected chemicals on the bakeite scale using the specified test protocol.

Example 1

Table 1, listed below, is the result of a specified test of carboxylic acid compounds. AM is 50/50 of 40% acrylic acid / maleic acid copolymer and has a MW of 4K to 10k. The C-810L fatty acid mixture is available from P & G Chemicals Inc. in Cincinnati, Ohio. FA / FAME is a mixture of commercial biodiesel by-products (available from Purada Processing, LLC, Lakeland, Florida) that is a C6 to C18 fatty acid / fatty acid methyl ester in a 60:40 ratio. Oxicure 300 is a fatty acid ester product available from Cargill, Inc. in Minneapolis, Minnesota. The EVA-MA copolymer is poly (ethylene-co-vinyl acetate-co-methacrylic acid), which is 25% vinyl acetate. LOP is a 100% flaxseed oil polymer prepared by thermal polymerizing flaxseed oil in the presence of maleic anhydride with pentaerythritol with additional crosslinking.

additive Dosage, ppm % I AM 500 54 C-810L Fatty Acid 1000 50 FA / FAME 1000 71 FA / FAME 500 30 Oxycure 300 1000 73 Oxycure 300 500 25 Polyacrylate (MW> 1M, Emulsion) 1000 20 Phthalic acid 1000 30 "Ester lower" (fatty acid, high MW) 1000 36 EVA-MA copolymer 1000 49 LOP 1000 43 LOP 500 14

Example 2

Table 2 below is the results for the specified tests of scale-inhibiting compositions comprising organic acid anhydrides and amides. OHS and OIS are 25% octadecenyl / 71% hexadecenyl-succinic anhydride and 47% octadecenyl / 47% isooctadecenyl-succinic anhydride, respectively. NDH is 1,8-naphthalenedicarboxylic acid 2-dimethylaminoethyleneamide hydrochloride.

additive Dosage, ppm % I OHS 1000 60 OIS 1000 54 Fatty acid anhydride 1000 59 NDH 1000 31

Example 3

Table 3, listed below, is the result for sulfonic acid scale-inhibiting additives using the specified test protocol. The approximate molecular weight of poly (styrenesulfonic acid-co-maleic acid), sodium salt of 1: 1 is about 20 kD. Dehsofix-920 is a naphthalenesulfonate-formaldehyde condensate, sodium salt (available from Tenneco Espana, St. Louis). Lomar D is a sulfonated naphthalene condensate, sodium salt (commercially available from Cognis Corp, Cincinnati, Ohio).

additive Dosage, ppm % I Poly (styrenesulfonic acid-co-maleic acid), sodium salt 1000 37 Dehsofix-920 1000 50 Lomar d 1000 51 1-octane sulfonic acid 1000 20

Example 4

The table below shows the results for scale inhibitors with amines in the polymer using the specified test protocol. Polymin® P is 50% crosslinked polyethyleneimine (commercially available from BASF® Corporation, Florham Park, NJ) with a molecular weight of about 70 kD. PEI-1 is a low molecular weight polyethyleneimine with 35% EDC-ammonia. PEI-2 is a high molecular weight polyethyleneimine with 35% EDC-ammonia. PEI-3 represents 23% solution of 60% carboxymethylated PEI-1 and PEI-4 represents 23% solution of carboxymethylated PEI-2. PDC is polyethyleneimine dithiocarbamate. Poly (DADMAC-co-NVP) is a 25% N-vinylpyrrolidone-diallyldimethylammonium chloride / 10% DADMAC copolymer.

additive Dosage, ppm % I Polymin® P 1000 37 2,2,6,6-tetramethyl-4-piperidinol 1000 38 PEI-1 1000 47 PEI-2 1000 33 PEI-3 1000 43 PEI-4 1000 36 PDC 1000 41 Poly (DADMAC-CO-NVP) 1000 28

Example 5

Table 5 listed below is the result of various mixtures of scale-inhibiting additives using the specified protocol test. AM and FA / FAME are as defined above. SX is 40% sodium xylenesulfonate. PP comprises 25% oxidized ethene homopolymer (polyalkylene-polycarboxylate), potassium salt; 9% ethoxylated nonylphenol; And 1% propylene glycol. TTP is 6% triethanolamine tri (phosphate ester), sodium salt; 9% acrylic acid-methyl acrylate copolymer, sodium salt; 3% ethoxylated tert-octylphenol phosphate; And 3% ethylene glycol-propylene glycol copolymer

additive Dosage, ppm % I SX & AM 500 each 54 SX & AM 250 each 31 PP & AM 500 each 18 TTP & AM 500 each 27 FA / FAME & AM 250 each 39

Example 6

Table 6 below shows the performance of various fatty acids and mixtures of fatty acids and fatty acid esters to inhibit scale formation using the test protocols mentioned and specified above. The nature and composition of fatty acid mixtures made from agricultural raw materials can vary considerably, including seasonal changes and changes expected when new suppliers are introduced. Successive individual fatty acids were tested and in individual experiments, fatty acid / methyl ester compositions from different suppliers were compared. The data indicate that changes in the composition will not have a significant impact on performance, and the optimal composition is generally about 1: 1 ratios of fatty acids and fatty acid methyl esters. This product is a liquid that provides good performance and can also be used in combination with polycarboxylates (high molecular weight fatty acids are generally solid or very viscous). The results indicate that changes in the composition of fatty acid / fatty acid ester mixtures from other agricultural raw materials will not affect performance.

TOFA 1 and TOFA 2 were light colored tall oil fatty acids prepared through partial distillation of natural tall oil (available from Georgia-Pacific Chemicals, Atlanta, Georgia, trade names XTOL® 101 and XTOL® 300, respectively).

chemical substance Dosage, ppm % I Experiment 1 Hexanoic acid 1000 66 Myristic acid 1000 22 Dodecanoic acid 1000 74 Stearic acid 1000 60 Nonanoic acid 1000 47 TOFA 1 500 95 Undecanoic acid 1000 57 FA / FAME 500 58 Heptadeconoic acid 1000 49 Palmitic acid 1000 46 TOFA 1 500 60 Experiment 2 TOFA 1 500 22 TOFA 1 1000 57 TOFA 2 500 40 TOFA 2 1000 55 FA / FAME 500 73 FA / FAME 1000 72 Experiment 3 Soft wood FA / FAME 1000 92 AM 1000 91 FA / FAME 1000 95 AM 1000 95 Experiment 4 Hardwood AM 1000 61 AM 1000 78 FAME 1000 90

Example 7

This experiment illustrates the performance of selected chemicals on the calcium carbonate scale using BLDM. Table 7 shows the results in the laboratory of calcium carbonate scale inhibition with comparative parameters (% contamination or “% F”) characterized by thermal conductivity. PP23-3389 and Scale-Guard® 60119 are commercial calcium carbonate scale inhibitors (commercially available from Nalco Company® in Naperville, Illinois). The BL of the evaporator from the Midwest plant, derived from the standard maple kraft, was used in this experiment.

Minutes % F of baseline 600 ppm PP23-3389 600 ppm 1: 1 Scale-Guard® 60116 350 ppm 1: 1 Scale-Guard® 60116 75 19.9 0 0.2 0 100 53 2.8 1.8 2.9 150 112.4 7.6 5.5 7.5 200 153.8 12.7 2.8 9.7 250 172.9 17.3 5.4 11.6 300 181.2 21.7 6.5 13.8 400 - 28.3 7.9 15.4 500 - - 8.9 17.6 1,000 - - 9.2 23.9

Example 8

BLDM was used to show the laboratory-test results of selected chemicals on the bakeite scale. Shown in Table 8 are the results from bakite scale inhibition in laboratory experiments. The BL source comes from the evaporator of the southern plant.

Minutes % F of baseline 1,000 ppm FA / FAME % F of baseline 1,000 ppm am % F of baseline 1,000 ppm 2: 1 AM-FA / FAME 30 272 193 109 65 123 43 60 432 277 154 110 N / A 75 120 N / A N / A 235 153 N / A 105

Example 9

In this example, the selected chemicals were tested in a factory setting using BLDM and deployed in a separate form. Table 9 shows the effect of scale inhibitors on bakite precipitation from field-test. The BL of the southern plant was used with the chemical supplied to the plant's conditions—hard wood, split batch, split line.

Minutes % F of baseline 1,000 ppm am 1,000 ppm FA / FAME 1,000 ppm 1: 1 AM-FA / FAME 300 21 5 10 One 500 33 8 15 4 600 65 * 9 20 5 800 - 13 30 8 1,000 - 21 - 15 1,100 - 25 - 20 1,200 - 88 * - 20 1,500 - - - 25 1,700 - - - 166 *

* Indicates exponential growth

It should be understood that various changes and modifications to the embodiments mentioned above will be apparent to those of ordinary skill in the art. Such changes and modifications may be made without departing from the scope and spirit of the invention and without diminishing its advantages. Accordingly, such changes and modifications are included by the appended claims.

Claims (15)

(a) measuring the precipitation level of the scale in an evaporator or concentrator of a pulp mill; (b) adding an effective amount of a scale-inhibiting composition to a black liquor (BL) if the measured level of precipitation of the scale exceeds a predetermined level; (c) the scale inhibiting composition comprises a monocarboxylic acid; Polycarboxylic acid; fatty acid; Low molecular weight and high molecular weight aromatic acids, low molecular weight and high molecular weight aliphatic sulfonic acids and aromatic sulfonic acids; Esters, anhydrides and their amides; Low and high molecular weight amines; And one or more compounds selected from the group consisting of combinations thereof; And (d) monitoring the concentration of the scale-suppressing composition in the waste fluid using an inert fluorescence tracker; Said waste liquor optionally having a solids content of less than about 50%; inhibiting scale precipitation from the waste liquor in an evaporator or concentrator of a pulp mill. The method of claim 1, (a) inserting a probe having a temperature-controlled outer surface into an evaporator or concentrator of a pulp mill; (b) contacting the temperature-controlled outer surface with the waste fluid; (c) measuring the thermal conductivity of the temperature-controlled outer surface, the thermal conductivity being determined by the amount of scale deposited on the temperature-controlled outer surface; (d) transferring the measured thermal conductivity to a controller; (e) determining the level of scale precipitated in the evaporator or concentrator of the pulp mill based on the measured thermal conductivity; And (f) if the measured level of scale precipitation exceeds the predetermined level, adding an effective amount of the scale-suppressing composition to the waste liquor. The method of claim 2, Intermittently or continuously measuring thermal conductivity on the temperature-controlled outer surface of the probe. The method of claim 1, Said scale comprising at least one scale selected from the group consisting of bakate, sodium sulfate, sodium carbonate, collected organic material, calcium carbonate, and combinations thereof. The method of claim 1, Based on the black liquor, adding about 1 to about 2,000 ppm of one or more compounds. The method of claim 1, The organic carboxylic acid, Acrylic acid-maleic acid copolymer in a ratio of about 1: 1 having a molecular weight of about 1,000 to about 50,000; Ethylene-vinyl acetate-methacrylic acid copolymer having a molecular weight of about 1,000 to about 50,000; Phthalic acid and other aromatic vic-dicarboxylic acids; Flaxseed oil polymer; Flaxseed oil polymer thermally polymerized in the presence of maleic anhydride and optionally cross-linked with pentaerythritol; And And a combination thereof. The method of claim 1, Wherein said organic carboxylic acid comprises one carboxylic acid or a mixture of fatty acids and / or fatty acid esters having a chain length of about C5 to about C50. The method of claim 1, The organic carboxylic acid, organic fatty acid and / or fatty acid ester, Adding an acid to the fatty acid salt solution of the natural fatty acid alkyl ester step; Adding an acid to the fatty acid salt solution of the natural glycerin step; Adding an acid to the stream of at least one biodiesel manufacturing process containing at least one fatty acid salt component; Performing a transesterification reaction with triglycerides; And And a biodiesel manufacturing process selected from the group consisting of combinations thereof. The method of claim 1, The organic carboxylic acid, organic fatty acid and / or fatty acid ester, And a component selected from the group consisting of methyl esters, ethyl esters, salts, methanol, ethanol, glycerin, water and combinations thereof. The method of claim 1, The organic carboxylic acid, organic fatty acid and / or fatty acid ester, C6 to C24 saturated fatty acids and unsaturated fatty acids; C6 to C24 saturated fatty acid salts and unsaturated fatty acid salts; Esters thereof having mono-, di- and trihydric alcohols of C1 to C6; And A process comprising at least one component selected from the group consisting of at least one inorganic salt. The method of claim 1, The organic fatty acid is selected from the group consisting of palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, arachidic acid, icosenic acid, Behanne acid, lignoseric acid, tetracosenoic acid and combinations thereof Characterized in that the method. The method of claim 1, The organic acid anhydride or amide, Octadecenyl / hexadecenyl-succinic anhydride; Octadecenyl / isooctadecenyl-succinic anhydride; Fatty acid anhydride mixtures; 1,8-naphthalenedicarboxylic acid amide; And And a combination thereof. The method of claim 1, The sulfonic acid is, Styrenesulfonic acid-maleic acid copolymer in a 1: 1 ratio having a molecular weight of about 1,000 to about 50,000; Sulfonated naphthalene-formaldehyde condensate; Alkyl-sulfonic acids having an alkyl chain length of about C5 to about C18; And And a combination thereof. The method of claim 1, The amine is, Linear or cross-linked polyethyleneimines having a molecular weight of about 1,000 to about 100,000; Carboxymethyl or dithiocarbamate derivatives of linear or cross-linked polyethyleneimine having a molecular weight of about 1,000 to about 100,000; N-vinylpyrrolidone-diallyldimethylammonium copolymer; 4-piperidinol; And And a combination thereof. (a) inserting a probe having a temperature-controlled outer surface into an evaporator or concentrator of a pulp mill; (b) contacting said temperature-controlled outer surface with waste fluid; (c) measuring the thermal conductivity intermittently or continuously on the temperature-controlled outer surface of the probe, the thermal conductivity being determined by the amount of scale deposited on the temperature-controlled outer surface; (d) transferring the measured thermal conductivity to a controller; And (e) determining the level of scale precipitated in the evaporator or concentrator of the pulp mill based on the measured thermal conductivity; scale from the waste liquid in the evaporator or concentrator of the pulp mill; To monitor the sedimentation.